Assessment Status Notes

Data Deficient (DD) based on the lack of knowledge on ecological requirements of the species. The status of Near Threatened (D) based on potentially small population can be argued if some restriction in habitat can be found.

Taxonomic notes

Psathyrella rhodospora is in a clade with Psathyrella spadicea and P. conissans (Padamsee 2008 thesis). The related P. spadicea was moved to the genus Homophron in 2015.
Psathyrella rhodospora has an irregularly convex cap up to 85 mm broad. It is light yellowish brown or yellowish white to pale light brown and has a white stipe. The grayish reddish brown spores on its gills distinguish it from other Psathyrellas, and occasionally spore deposits can be seen on its cap. Smith (1972) mentions that it resembles P. variata but can be distinguished by its broad gills, 5-6 mm wide. This species also resembles P. sublateritia, which has a medium reddish brown spore print, but P. sublateritia is concentrically zoned with bands of brownish pink and light reddish brown when fresh. Microscopically, P. rhodospora can be separated statistically from P. sublateritia, which has longer basidiospores. The ITS data separates P. rhodospora from P. sublateritia Padamsee (2001).

Why suggested for a Global Red List Assessment?

Psathyrella rhodospora was listed as an endangered species in Minnesota in 1996, and thought to be endemic to Minnesota. First found in 1971, it was not reported elsewhere. Focused research on Psathyrella during 1998 to 2007 has documented Psathyrella rhodospora for a total of 5 sites in Minnesota. There are a limited number of reddish-spored Psathyrella species so this mushroom could be sought for by professional and amateur mycologists in America.

Geographic range

Known from five sites in Hennepin, Ramsey, and Rice Counties in Minnesota, USA.

Population and Trends

The species is known from 5 sites in 3 counties in Minnesota, USA. Psathyrella rhodospora was first collected in 1971 in Rice County near Nerstrand Woods State Park. Focused research on Psathyrella, 1998 to 2007, found it repeatedly at 2 other sites: one site in Hennepin County in 1998, 1999, and 2001 (McLaughlin 1998), and at three sites in Ramsey County in 2003, 2004, 2005, 2006 and 2007 (see MycoPortal.org). Its population size appears to be very small and its known distribution extremely limited.
The population could be considered as two subpopulations separated by 70 km, the original area in Rice County and the new sites in adjacent Hennepin and Ramsey Counties. The estimated population size is 4000 mature individuals factoring in the potential distribution in surrounding states: 2 known subpopulations × 10 functional individuals (genets) per subpopulation × 10 mature individuals (ramets) per genet × a factor of 20 for potential sites. This site uncertainty could be greatly reduced if intense surveys could be carried in surrounding states.

Population Trend: Uncertain

Habitat and Ecology

Psathyrella rhodospora was originally found on the stump of a Tilia americana (basswood) tree. The more recent finds have been on and beside a large, undecayed Populus deltoides ssp. monilifera (cottowood) stump located on a bank above the Mississippi River (McLaughlin 1998) and at the base of a living Populus deltoides located on the St. Paul campus of the University of Minnesota. Also found at base of Ulmus americana.
Not much is known about the biology of P. rhodospora. It is possibly a saprotroph on wood, although its resource specificity is not known. The species is found on or beside the stumps of deciduous trees but also at the base of living trees. It is not restricted to dead stumps, thus it could be something other than a saprotroph, but we lack proof of this as it might only be growing on dead roots.
It is usually found in small groups or scattered. It may fruit in successive years, based on recent scientific observations. A search for this mushroom in the same site one year later relocated the species, but it was a smaller collection (McLaughlin 1999). At present it seems best to preserve the associated tree stump, as it is not known how important this is for fruiting. Psathyrella rhodospora is likely dispersed in the form of mycelia (thread-like structures that make up the body of a fungus) and spores. Low nutrient availability probably triggers the growth of the mushroom in this species. The earliest documentation of this species is the 13th of June and the latest is the 10th of October. Because P. rhodospora has only been reported from five sites, it is difficult to specify its life history. Additional studies should reveal more information about its biology.

ForestTemperate Forest

Threats

Threats would include loss of suitable habitat and substrates by development and removal of dead wood or associated hardwood trees.

Conservation Actions

There are no past or current conservation actions for this species. Psathyrella rhodospora as unclear ecology being associated with living trees and also recently dead hardwood trees with the bark intact. Unlike several other rare fungi species in Minnesota, it has not been observed with Quercus spp. (oak). Its conservation may require preserving habitat where it is found as well as comparable hardwood areas and forests where recently dead trees are allowed to decay undisturbed. If further populations of the species can be found then protective conservation actions can be considered.

Site/area protectionSite/area managementAwareness & communications

Research needed

Surveys for P. rhodospora have been conducted in four counties with searches based in Nerstrand Woods State Park, Afton State Park, Wolsfeld Woods Scientific and Natural Area, Belwyn Educational Center, and the Minnesota Valley National Wildlife Refuge. Research has been conducted on the separation of P. rhodospora from P. sublateritia (Padamsee 2001).
Surveys are needed to search for other potential populations and to monitor the known location of this species. Based on previous collections, the best time to search for P. rhodospora in Minnesota is from June through mid-September. There are a limited number of reddish-spored Psathyrella species so this mushroom could be sought for by professional and amateur mycologists in America.